Up to now, the operator has carefully vacuumed all the swarf and other bits from the bottom of the tubing. This method is somewhat empirical and does not guarantee effective protection of the circuits after the installation is back in operation. Further, it is necessary to isolate, empty, and cool the portion of tubing in which the work is to be performed. All these operations are lengthy and expensive in manpower. They require the installation to be closed down for a relatively long period of time.
In other applications a scraper piston is used by inserting it at one end of the tubing and by moving it along the tubing to its other end. As it moves along, the piston sweeps any foreign matter present in the tubing. This solution, however, is only of interest for long lengths of tubing, and in any case it is difficult to use for a spot check under a controlled atmosphere, since the tubing has to be freed over its entire length and opened at both ends.
In contrast, preferred embodiments of the device provided by the present invention enable circuits to be kept under a controlled atmosphere of inert or neutral gas by sealing the tubing from its surroundings throughtout the operations. They also enable work to be performed while the tubing is still hot (after the tubing has been emptied, it remains at a temperature close to that of liquid sodium, i.e. about 180.degree. C.) by localizing operations to the work zone and by avoiding the need for the operator to thoroughly inspect the inside of the tubing for foreign matter.